听力原文： A new data shows nations in every part of the world, 51 in all, are suffering declining life expectancies because of an increasing prevalence of HIV infection. The impact is occurring in Asia, Latin America and the Caribbean, but is greatest in sub-Saharan in Africa, with only 10% of the world's population, but 70% of its HIV infections. Seven African countries have life expectancies of less than forty years. For example, in Botswana, life expectancy is 39 years. By 2010, it will be less than 27 years. Without Ali)S, it would have been 74 years. In such Asian countries as Cambodia and Burma, life expectancies are predicated to decline to around 60 years from what would have been in the mid-sixties. Even in countries where the number of new infections is dropping, such as Thailand, Uganda and Senegal, small life expectancy drops are forecast. Which of the following regions in the world will witness the sharpest drop in life expectancy?